The invention concerns a silicon micromechanical weight sensor.
Weight sensors fabricated by silicon micromechanical techniques for gauging static gravitational force have not been disclosed in the prior art. Other types of miniature weight sensor structures suffer from instability problems caused by such factors as, e.g., the long-term instability of the mechanical or electrical construction of the sensor.
It is an object of the present invention to overcome the disadvantages of the above-mentioned prior art and to provide an entirely novel type of silicon micromechanical weight sensor.
The goal of the invention is achieved by virtue of fabricating a capacitive weight sensor by micromechanical processes from monocrystalline silicon. Particularly advantageously at least the spring element of the weight sensor is made from monocrystalline silicon.
More specifically, a silicon micromechanical weight sensor according to the invention is characterized by what is stated in the characterizing part of claim 1.
The invention provides significant benefits.
A capacitive weight sensor based on micromechanical machining from monocrystalline silicon offers an advantageous construction owing to its highly stable structural properties, small size and low production costs. It may be proved by computations means that a weight sensor according to the invention can weigh a mass of one gram with an accuracy of one millionth part per gram, and even better.
The invention provides important practical benefits stemming from its capability of weighing very low masses and the novel measurement method used therein.
Furthermore, the disturbing effect of external vibrations is eliminated by a relatively high mechanical resonant frequency and use of force feedback applied on the sensor electrodes.